In many sectors of industry there is a need for conductive pigments which can be used, for example, to produce plastics, lacquers, coatings or fibers or the like which are electrically conductive or antistatic or which screen against electromagnetic waves. Conductive carbon black is employed for this purpose in large amounts and yet because of its high light absorption cannot be used for pale or colored coatings. A further disadvantage is the strong absorption of carbon black in the IR region, which in the case, for example, of solar irradiation leads to frequently unwanted warming of the coated articles.
For pale conductive coatings, therefore, the use of doped metal oxides, especially antimony-doped tin oxide, is on the increase.
U.S. Pat. No. 5,472,640 describes conductive platelet-shaped pigments: a platelet-shaped substrate coated with one or more metal oxide layers is coated with a conductive layer of antimony-doped tin oxide, with a thin SiO.sub.2 layer disposed between the conductive layer and the metal oxide layer.
U.S. Pat. No. 5,350,448 discloses a pale, electrically conductive pigment consisting of a platelet-shaped substrate and halogen-doped tin and/or titanium dioxide as the conductive layer. The specific resistance of the pigment is given as less than 25 k.OMEGA.cm.
DE 44 35 301 describes electrically conductive pigments having a phosphorus-doped tin oxide layer as a conductive layer on a substrate. The specific resistance of the pigments is given as less than 10 k.OMEGA.cm.
The pale conductive pigments of the prior art have levels of electrical conductivity which fail to satisfy the stringent requirements of certain conductive coatings.